This invention relates in general to seals and, more particularly, to a method of installing a cartridge-type seal on a pump or other casing through which a shaft extends and a method and tool for resurfacing such a casing.
Many pumps in operation today, particularly those for pumping water, have packing-type seals between their casings and impeller shafts. In the typical pump, the packing-type seals fit within stuffing boxes that are actually circular sockets in the casing. During operation of the pump the seals absorb a slight amount of the liquid that is circulated by the pump, and in so doing expand to create a reasonably effective barrier along the shaft and the stuffing box of the casing. Since the packing of the seals must remain moist, the seals continually leak, and although the amount of the leakage is quite small, it does occur. This causes corrosion at the stuffing boxes and on the outside of the casing. Moreover, the packing of the seals must bear against the shaft with considerable force, this force being supplied by rings or glands that are bolted tightly to the casing and around the shaft to compress the packing in the stuffing boxes. The force exerted by the packing on the shaft ultimately causes fretting and grooves to develop in the shaft.
Cartridge-type seals are currently available as replacements for the old packing-type seals, and although they are more costly than packing seals, they are considerably more durable and eliminate the foregoing problems associated with packing-type seals. The typical cartridge-type seal has a sleeve that revolves within a flange and between the two is a seal element made from an extremely durable material. The flange is attached to the casing with the same bolts that were formerly used to secure the gland that compressed the packing, there being a gasket between the two to provide a static seal. The sleeve, on the other hand, is secured to the shaft with a set screw, and to prevent leakage along the shaft surface, the sleeve contains several O-rings that bear against the shaft surface and form static seals between the inside of the sleeve and the shaft. The live seal between the rotating shaft and the stationary casing exists at the seal element which is within the flange and around the sleeve.
While cartridge-type seals may be fitted to many pumps with little effort, on others the installation is a major undertaking. In this regard, some pumps, particularly the older ones, are badly corroded in the regions of their packing-type seals, and do not provide surfaces that are flat enough or true enough to bolt the flanges of cartridge-type seals against them. In these instances, the pump must be disconnected from its supply and discharge pipes and thereafter disassembled. Its casing is further removed from the foundation on which it rests and delivered to a machine shop where it is machined in the regions surrounding its stuffing boxes so as to provide surfaces that are flat and perpendicular to the shaft axis. Thereafter, the casing is replaced on and secured to its foundation and the supply and discharge pipes are reconnected to it. Finally, the pump is assembled with the cartridge-type seals in lieu of the packing-type. This procedure consumes a considerable amount of time and requires skilled mechanics. As such it is quite costly.